1

Selected Highlights of the First Workshop Goals for the 2nd Workshop

HERA and the LHC 2nd workshop on the implication of HERA for LHC

physics

A De Roeck (CERN) Lisbon 29/06/06

2

Examples: HERA LHC

Structure functions and parton distributionsLHC: cross sections/precision

Underlying event:tunable elementarityof one beam particlep *p collisionsLHC: event complexity

B-production: B quark PDFs of the protonLHC: Higgs production

DiffractionLHC: diffractivescalar production

3

Workshop Aims

Five Working Groups Parton density functions Multi-jet final states Heavy quarks (charm and beauty) Diffraction MC-tools

Workshop Chairs H. Jung, ADR

6 major meetings in 12 months

http://www.desy.de/~heralhc

4

Many thanks to all conveners and authors !

hep-ph/0601012hep-ph/0601013

Available on request from CERN/DESY libs

>650 pages

– Phase I of this workshop concluded with

the proceedings– However an important link between

communities has been established.– March 05’: We should not just let it fade

away, but strongly exploit it, to the benefit of both communities.

– Therefore keep momentum with one HERA/LHC meeting per year

– Keep also good contacts with TeV4LHC workshop activities (started Sept.2004)

2006 CERN: 6-9 June2007 DESY March or May/June 072008 CERN (first LHC physics? )

Proceedings

June Workshop: 17 plenary talks 80 parallel talks

6

PDFs & ADD extra dimensions: di-jet final state

Reduction of the sensitivity due toPDF uncertainty (CTEQ6)

Graviton exchange contributions reduce the cross section (interference)

S. Ferrag

7

Impact of Future HERA Data

Improvement in PDFprecision with projected700 fb-1 of data in HERA-II

Includes jets in DIS and p

Note only HERA (ZEUS) data are used in the fits

GwenlanCooper-SarkarTargett-Adamshep-ph/0509220

9

From M. Cooper-Sakar, C. Gwenlan and S. Glazov

Much reduced uncertainties .... Model independent analysis of data desirable

get THE HERA – PDF !!!!!

● Combined PDF fit to H1& ZEUS ● Average H1&ZEUS data sets

Average HERA data

10

LHC Kinematics/QCD evolution

Evolution of PDFs to high Q2 & low x important at the LHCPrecision? Level of approximation? CCFM/BFKL?, non-linear effects?

11

Impact of the measurement of FL

FL could referee the gluon distribution! FL is like F2: little theoretical ambiguity (compared to e.g. F2

C)

H. Stenzel R. Thorne

),()(),(])1(1/[ 222

222 QxFyfQxFFyyF LLr

Need to lower the energy of proton or electron beam for this measurement

See J. Feltesse

12

Measuring FL

Detailed study for H1, with 2 lower proton beam energy settings

FL can refereebetween MRSTand CTEQ gluons

FL is gluon driven

FL measurement in 2007 !

CTEQ

MRST

Feltesse/Klein et al

13

• A good preparation for the LHC start needs also to include:realistic simulations to optimize data analysis and data interpretationsneed to investigate and identify final states where accurate x-section measurements/calculations can be made

• Find a realistic interactive (HERA-LHC) strategy to constrain PDF's

• Experimentalists and theorists have to “learn” how to measure and calculate the same things !

• Should form a “group” from ATLAS, CMS, LHCb, ALICE, H1, ZEUS and theoretical PDF experts

M. Dittmar

PDF Group plans (summary)

14

~ 105 c+b events in 10 fb-1 with pt

muon >10 GeV

xc,xb probed in 0.05<xc,xb<0.1 with 10% stat.accuracy

xs ~0.1 for 10 fb-1 with 10% stat. accuracy

• need u,d uncertainties

• simulation of final state including frag.fct and PS

strange quark PDF

charm quark PDFK. Mazumdar et al

PDF determination at LHC

See also talk on M. Cooper

16

Proton AntiProton

Multiple Parton Interactions

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Outgoing Parton

Outgoing Parton

from R. Field

What is the underlying event (UE), multiple parton interactions (MI)?Everything, except the LO process we're currently interested in

• parton showers• additional remnant – remnant interactions

Do Tevatron tunes work at HERA?

Underlying event/multiple interactions

17

Pythia 6.214ATLFAST 602

Effect of underlying event on central jet veto in VBF HiggsEffect of underlying event on central jet veto in VBF Higgs

Uncertainty of the central jet vetoefficiency due to UE model; ATLAS.

Rapidity of the central jet in Higgs events; CMS; full simulation, L=2x1033cm-2s-1

“bkg. like” behaviour for soft jets; fake jets: pile up+UE+detector

H->WW*->2lH->WW*->2lin qqH prod.in qqH prod.

18

Initial kT at HERA and LHC

Higgs

Initial kT in the hard scatteringCascade calculation

<kT> large unintegrated parton PDFs will be needed Test predictions at HERA Large kT effects affect Higgs searches Measure unintegrated PDFs f(x,Q2,kT

2) at HERA via final states

Jung

19

Non-linear effects at LHC

estimates for ALICE

×

Nonlinear evolution equation for uPDF: (Balitsky-Kovchegov equation)

A. Dainese et al

Bottom suppression due to non-linear effects in BK

●Significant effects...●up to factor of 2 in hot spot scenario ●factorization still ok ?

20

HERA II analysis (expect factor 10 more), larger kinematic range➔ Understand b-production mechanism (...remember b-puzzle at the

TeVatron...)➔ NOTE: gluon drives heavy quark PDFs .... transverse momenta ????

Current H1 (HERA I) analysis From O.Behnke, A. Geiser, A. Meyer, M. Wing

beautycharm

HERA: Heavy Quark PDFs at large Q2

21

A. Mitov

• Leading uncertainties are:scales & fragmentation

Can these uncertainties be reduced ?pert. corr. known to NLO. NNLO is hard, but feasible (work started...)fragmentation is presently refined at NLL level

Important also for top mass measure: B-meson and lepton

charm at LHC b at LHC

Uncertainties in HQ production

22

Hgap gap

b

b -jet

-jet

Exclusive Higgs ProductionExclusive diffractive Higgs production pp p +H+ p : 2-10 fbCross section ‘stabelized’ during the previous workshop

p p

beam

p’

p’roman pots roman pots

dipole

dipole

22 )''( ppppM H

Advantages Exclusive: Jz=0 suppression of ggbb background Mass measurement via missing mass

E.g. V. Khoze et alM. Boonekamp et al.B. Cox et al. …

M = O(1.0 - 2.0) GeV

Experimental effort startedSee B. Cox

23

• Idea to fill gap in rapidity with calorimeter at 135 m in front of TAN ( E ~ 2.0 - 5.5 TeV and pseudorapidity range 8 – 12 )

• Beamline simulation performed• Pseudorapidity resolution ~ 0.25-

0.5 ( depends on the selected energy rapidity range)

• Radiation level near the calorimeter at 135 m is reasonable (from studies of ZDC)

• Tracker in front of calorimeter to improve coordinate resolution (GEM)

V.Andreev, A.Bunyatyan, K.Borras, HJU, M.Kapishin, L.Lytkin

Ideas for upgrading forward region

24

MC and other Tools

• Parton distribution library:– LHAPDF now official carrier of the PDFs

• Used by LHC experiments in generators• HERA pdfs have been added• Allows error uncertainty estimates• Pion and photon added, particularly for HERA. F2D next?

• NLOLIB framework for NLO QCD programs– Uniform user interface/interface to HZTOOL– e+e-/ep included, pp can be added

• HZTOOL/JetWeb/RunMC/Cedar(?) for tunning – All HERA results to be included, some e+e-. Include more pp?

• RAPGAP, Cascade Monte Carlos for inclusive and diffractive pp• Plenty of exchange on other MC tools, leading to new MC tools and

comparisons with ep where possible • Continuation of the MC@LHC 2003 workshop , concerning

validation A new MC@LHC workshop this summer 2006: July 17-26

25

Nutshell: Results from HERA/LHC I• Parton Distribution Functions

– Dialogue/discussion between PDF fitters and community that delivers the data.

– Combined data (H1/Zeus Datasets for F2, F2D), other data (e.g. TeV. jets)?– Discrepancies between PDFs will be ironed out, eg via to new

measurements. Fits with 1- bands available.– Quantitative estimates for low-x/large-x resummation available – Timescale for the full program 1-2 years, i.e. just in time for the LHC Will lead to more precise PDFs: maybe factor 2? (personal

guess/hope)

• Diffraction– Improved understanding on the DPE/Higgs production and cross section

• Final states– Lots of work/progress on underlying events (tuning), gap survival

• Heavy quarks– Saturation effects measurable at low pt– Heavy quark parton distributions eg. for Higgs cross section calculations.

• Tools– Tool developments ongoing strongly…

26

• PDF determination:– Best possible PDF – Uncertainties on the PDF and evolution– Special PDFs? Diffractive, unintegrated, generalized..

• Event topologies:– Multiple Interactions– Underlying Events– Higher Order Corrections

• Reliable Simulations/ Theory/Models– tuning of free parameters to many different measurements– improved calculations– alternative approaches

Keywords: tools, phenomenological progress, and quantitative estimate for the impact of HERA on LHC measurements

What LHC needs for start in 2007 ?

Goals for HERA/LHC II

27

MC - ToolsS. Gieseke, F. Krauss,T. Kluge, P. Bartalini,P. Robbe, S. Chekanov

Multijets & final statesUnderlying events,un-integrated pdfsL. Lonnblad, G. Zanderighi, C. Gwenlan, N. Tuning, S. Banerjee, Ch. Risler, D. Traynor

Structure functions and parton distributionsS. Forte, S. Moch,M. Dittmar, A. Glazov M. Botje

DiffractionM. Diehl, V. Khoze M. Arneodo, P. Newman,A. Bruni, B. Cox, R. Orava

Heavy quarks: B quark pdfs of the proton, fragmentation fct, u-pdfs M. Cacciari,H. Spiesberger, A. Dainese, A. Geiser, K. Lipka,U. Uwer

Working Groups of the workshop

28

Backup

29

non-linear (quadratic) correction

has “–” sign

➔ Q2 evolution is slower

refit HERA F2 data, reduces F2DGLAP at

low x and moderate Q2

xg(x,Q2) at low Q2 (<10 GeV2) and

x (<10-3) is larger than in DGLAP

➔ Get these non-linear effects better understood from HERA !➔ Precise HERA data important !!!➔ connection to MI, diffraction ...

estimates for ALICE

@xg(x;Q 2)@logQ 2 =

@xg(x;Q 2)@logQ 2

¯¯̄¯D GLAP

¡9¼®2s2Q 2

Z 1

x

dyyy2G (2)(y;Q 2)

x2G (2)(x;Q 2) =1

¼R 2

¡xg(x;Q 2)

¢2

A. Dainese et al

GribovLevinRyskin-MuellerQiu equation:

Deviations: non-linear effects in QCD evolution?

30

proton proton collider LHC √s = 14 TeV

LHC: Higgs, SUSY etc, but mostly QCD...

electron proton collider HERA √s = 320 GeV

HERA: QCD structure of the proton

rQ 2

s» 0:01

rM 2

s» 0:01

forM » 140GeV

typical range

Why HERA and the LHC?

31

Extra Dimensions?

Supersymmetry?

Signature for new physics➔ jet x-section

Discovery potential dependson precise PDFs

Precision determination of PDFs needed ... understanding QCD is the key to new physics

inclusive jet xsection D.Stump et al hep-ph/0303013

CTEQ6 uncertainties

Precise PDFs for the LHC

CTEQ6.1

32 Monika Grothe, CMS diffractive and forward physics program, June 2006

Low lumi Rapidity gap selection possibleHF, Castor, BSCs, T1, T2Proton tag selection optionalRPs at 220m and 420 m

Diffraction is about 1/4 of tot

High cross section processes“Soft” diffractionInteresting for start-up runningImportant for understanding pile-up

High lumiNo Rapidity gap selection possibleProton tag selection indispensableRPs at 220m and 420 m

Central exclusive productionDiscovery physics:Light SM HiggsMSSM HiggsExtra dimensions

Gamma-gamma and gamma-proton interactions (QED)Forward energy flow - input to cosmics shower simulationQCD: Diffraction in presence of hard scale Low-x structure of the proton High-density regime (Color glass condensate) Diff PDFs and generalized PDFs Diffractive Drell-Yan

Low

lu

mi

Hig

h lu

mi

CMS + Totem + FP420

M. Grothe

33

• goal: mass resolution 1 GeV for Higgs with

• 420 m stations are needed for low mass Higgs

• other issues:triggersgap-survivalrates

• Detector stations at 220 m and 420 m from Interaction point

• 420 m station is in cold region.... – Hamburg pipe

420 m 220 mm Higgs= 160GeV

m Higgs< 200GeV

B. Cox, M Grothe, H. Kowalski et al.

Measurement of exclusive Higgs

34

Parton Density Functions and all that

• collinear PDFs

• uPDFs (single and double unintegrated)

• diffractive and generalised PDFsExclusive Higgs

production

35

Topics

Parton Density Functionsand all that...

(assuming we have the proper theory)

Event Topologies and all that ...

(going beyond the well known ... )

36

Monte Carlo and Tools

• Include also LEP data• Provide tuning including

HERA, LEP and TeVatron data !!!

C. Risler, J Butterworth

HZtool• calculate and compare predictions

with measurements➔ MC generators, NLOlib, MC@NLO➔ useful for tuning of parameters➔ useful for PDF fits with final states

➔ includes HERA, LEP, TeVatron data➔ will be coupled to HEPDATA➔ will develop into RIVET (Robust

Independent Validation of Experiment and Theory) a C++ version of HZTool. Work started !

➔ MC/NLO validation ➔ compare to very different

measurements

Request by HERA & TeVatron & LHC:

➔ include all available infos for benchmarking, validation and tuning

example for tuning: ARIADNE parameters with new PDFs

compare to fwd jet xsection (not used in tuning) (A.

Knutsson, L. Joensson)

37

FP420

TOTEM

xL=P’/Pbeam=

FP420

CMS IP T1/T2, Castor, BSC ZDC RPs@150m RPs@220m

possibly detectors@420m

Nominal LHC beam optics, * =0.5m: TOTEM: 0.02 < < 0.2 FP420: 0.002 < < 0.02

M. Grothe

FP220 and FP420 program also in ATLAS !!!

38

Exclusve Higgs production, again...

• Numerous papers by V. Khoze, A. Martin, M. Ryskin, A. Kaidalov, J. Stirling:

New investigation of rescattering effects by L. Motyka, J. Bartels,

S. Bondarenko, K. Kutak

L. Motyka: • First correction due to hard rescattering are large, and negative • need to perform resummation• Durham assumption of factorization of hard production and

soft rescattering does not hold, unless special cancellations occur

➔ Needs further clarification

L. Motyka

39

• precision determination of PDFs, including uPDFS and generalised PDFs

– what precision can be expected in 2007/2008 from the HERA and perhaps combined with other data and with the improvements in theory? This was started in the first workshop but is it the final word for LHC preparation

– how does it affect LHC measurments quantitatively– combined H1/ZEUS parton data sets (started at the previous)– can we judge which PDF is preferred (MRST/CTEQ...) in 2007/2008

eg.from FL or LHC measurements?• MI/underlying events/jets

– uncertainties for top/Higgs production– underlying event tuning at HERA (as for the Tevatron data)

• testing new underlying event models with data• new advised parameter set for underlying events

– Quantative uPDFs and MI influence for SUSYHiggs discoveries– Understanding MI interactions with HERA data (AGK,…)– uncertainties for gap-survival probabilities for the LHC– Test HO/resummed jet predictions at HERA

Goals and suggestions for 2nd workshopH. Jung/ADR

40

• Heavy Quarks: details of production mechanisms– beauty at HERA -> top at LHC ?– higher orders– small x/ large x resummations– saturation effects– Include HERA charm data for gluon constraints in fits (like the jets)

• diffraction and small x– saturation and non-linear effcts:– what is the saturation scale, where HERA can help– is saturation relevant for LHC, and where ?– physics of the forward region– elastic protons– jets in 6 < eta < 11– what can be learned from total xsection sigma_tot for ptcut in multiple

scatterings ?– How to relate diffraction with multiple scatterings – continuing studies on the exclusive Higgs production and detection

Goals and suggestions for 2nd workshop

41

MC & Tools - HZTool -> relevanca also for MC@NLO - benchmarking of xsections for HERA and LHC: jets, W/Z, Higgs, HQ,

diffraction - Tools for pdf fits including proper treatment of alphas, different evolution

(DGLAP LO/NLO/NNLO, CCFM/BFKL) proper treatment of data uncertainties extraction of PDFs, uPDFs, generalised PDFs

- NLO programs and libraries - SCET type of QCD generators for multi-jet production?

Keywords: tools, phenomenological progress, and quantitative estimate for the impact of HERA on LHC measurements

Goals and suggestions for 2nd workshop

42

Physics at the LHC: pp @ 14 TeV

j1j2

b-jett

W

Higgs!

Supersymmetry?

Extra Dimensions?

Precision measurementse.g top!

QGP?

But also QCD, diffraction, b & c physics,… especially in the early phaseThese need to be understood for precision measurements, bkg understanding etcImportant role for HERA data & HERA expertise This workshop

CP triangle!

Split SUSY?

43

Physics at the LHC: other examples

QCD @ LHC in its own!!!QCD @ LHC in its own!!!High scale QCD, jets, UHECR, smallest x, High scale QCD, jets, UHECR, smallest x,

parton saturation - new phase in QCD - non-linear phenomenaparton saturation - new phase in QCD - non-linear phenomena

Multi Jet event:Is it Multiple Interaction or Black hole production

High energy hadron showers

Color glass Condensate

UHE CR

LHC

44

Multiple Interactions at LHC

• Models tuned to TeVatron datagive HUGE differences at LHC ... better understand multiple interactions ...

Charged multiplicities in transverse region C. Buttar et al

pt > 0:5 GeV; j́ j< 1

45

Towards understanding of MI

• Cutting rules (AGK) extended to QCD

• Relate diffraction, saturation and multiple scatterings

• All from the same amplitude, but different factors:

– +1 Diffraction– - 4 Saturation– +2 Multiple Interactions

• Extended now also to pp !!!!– further work needed ...

➔ HERA is the place to understand MI !!!! (TeVatron to tune MC !!!)

➔ Towards the description of “everything” !!!!!

Bartels, Kowalski, Sabio-Vera

46

Multiple Interactions and top mass

● Multiple Interactions● Jet fragmentation properties, jet profiles● Final state QCD radiation● B-fragmentation

j1j2

b-jet

t

W

Significant effects on top mass determinationBetter understand them !!!

hep-ex/04003021

from M. Mangano

Are we sure ?

47

WG1: PDFs

Simple spread of existing PDFs givesup to 10% uncertainty on Higgs cross section we have to do better than that!

48

DGLAP evolution

At the LHC: momentum fractions x1 and x2 determined by mass and rapidity of X

HERA measurements do not cover the LHC region, eg. for central Higgs productionPDFs evolved via DGLAP equations from (x,Q2

0) to (x,Q2)

Note: W,Z, Higgs production needs PDFs from the x range 10-4 – 10-1

Is it safe?Q. is NLO (or NNLO) DGLAP sufficient at small x? Are higher-orders ~ αS

n logm x important? CCFM? BFKL? Non-linear effects? Saturation?

QCD Evolution of PDFs

E.g. R. Thorne: yes low-x resummations are important and can lead to >10%differences

49

• Next HERA-LHC workshop (before LHC starts)

Spring 2007 at DESY

(exact dates still to be decided)• informal meetings/working group

weeksfall 2006 and/or Jan 2007

• Proceedings after 2007 meeting – contributed papers for 2006 are still

accepted and electronically published

• 2008 meeting at CERN with first results from LHC

• Contributions are still possible and welcome !

Continued

this not the end